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mirror: Switch mirror_do_read() to byte-based

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We are gradually converting to byte-based interfaces, as they are
easier to reason about than sector-based.  Convert another internal
function, preserving all existing semantics, and adding one more
assertion that things are still sector-aligned (so that conversions
to sectors in mirror_read_complete don't need to round).

Signed-off-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Eric Blake 2017-07-07 07:44:50 -05:00 committed by Kevin Wolf
parent 782d97efec
commit ae4cc8777b
1 changed files with 33 additions and 41 deletions
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74
block/mirror.c
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@ -196,7 +196,7 @@ static inline int mirror_clip_sectors(MirrorBlockJob *s,
/* Round offset and/or bytes to target cluster if COW is needed, and
* return the offset of the adjusted tail against original. */
static int mirror_cow_align(MirrorBlockJob *s, int64_t *offset,
unsigned int *bytes)
uint64_t *bytes)
{
bool need_cow;
int ret = 0;
@ -204,6 +204,7 @@ static int mirror_cow_align(MirrorBlockJob *s, int64_t *offset,
unsigned int align_bytes = *bytes;
int max_bytes = s->granularity * s->max_iov;
assert(*bytes < INT_MAX);
need_cow = !test_bit(*offset / s->granularity, s->cow_bitmap);
need_cow |= !test_bit((*offset + *bytes - 1) / s->granularity,
s->cow_bitmap);
@ -238,59 +239,51 @@ static inline void mirror_wait_for_io(MirrorBlockJob *s)
}
/* Submit async read while handling COW.
* Returns: The number of sectors copied after and including sector_num,
* excluding any sectors copied prior to sector_num due to alignment.
* This will be nb_sectors if no alignment is necessary, or
* (new_end - sector_num) if tail is rounded up or down due to
* Returns: The number of bytes copied after and including offset,
* excluding any bytes copied prior to offset due to alignment.
* This will be @bytes if no alignment is necessary, or
* (new_end - offset) if tail is rounded up or down due to
* alignment or buffer limit.
*/
static int mirror_do_read(MirrorBlockJob *s, int64_t sector_num,
int nb_sectors)
static uint64_t mirror_do_read(MirrorBlockJob *s, int64_t offset,
uint64_t bytes)
{
BlockBackend *source = s->common.blk;
int sectors_per_chunk, nb_chunks;
int ret;
int nb_chunks;
uint64_t ret;
MirrorOp *op;
int max_sectors;
uint64_t max_bytes;
sectors_per_chunk = s->granularity >> BDRV_SECTOR_BITS;
max_sectors = sectors_per_chunk * s->max_iov;
max_bytes = s->granularity * s->max_iov;
/* We can only handle as much as buf_size at a time. */
nb_sectors = MIN(s->buf_size >> BDRV_SECTOR_BITS, nb_sectors);
nb_sectors = MIN(max_sectors, nb_sectors);
assert(nb_sectors);
assert(nb_sectors < BDRV_REQUEST_MAX_SECTORS);
ret = nb_sectors;
bytes = MIN(s->buf_size, MIN(max_bytes, bytes));
assert(bytes);
assert(bytes < BDRV_REQUEST_MAX_BYTES);
ret = bytes;
if (s->cow_bitmap) {
int64_t offset = sector_num * BDRV_SECTOR_SIZE;
unsigned int bytes = nb_sectors * BDRV_SECTOR_SIZE;
int gap;
gap = mirror_cow_align(s, &offset, &bytes);
sector_num = offset / BDRV_SECTOR_SIZE;
nb_sectors = bytes / BDRV_SECTOR_SIZE;
ret += gap / BDRV_SECTOR_SIZE;
ret += mirror_cow_align(s, &offset, &bytes);
}
assert(nb_sectors << BDRV_SECTOR_BITS <= s->buf_size);
/* The sector range must meet granularity because:
assert(bytes <= s->buf_size);
/* The offset is granularity-aligned because:
* 1) Caller passes in aligned values;
* 2) mirror_cow_align is used only when target cluster is larger. */
assert(!(sector_num % sectors_per_chunk));
nb_chunks = DIV_ROUND_UP(nb_sectors, sectors_per_chunk);
assert(QEMU_IS_ALIGNED(offset, s->granularity));
/* The range is sector-aligned, since bdrv_getlength() rounds up. */
assert(QEMU_IS_ALIGNED(bytes, BDRV_SECTOR_SIZE));
nb_chunks = DIV_ROUND_UP(bytes, s->granularity);
while (s->buf_free_count < nb_chunks) {
trace_mirror_yield_in_flight(s, sector_num * BDRV_SECTOR_SIZE,
s->in_flight);
trace_mirror_yield_in_flight(s, offset, s->in_flight);
mirror_wait_for_io(s);
}
/* Allocate a MirrorOp that is used as an AIO callback. */
op = g_new(MirrorOp, 1);
op->s = s;
op->offset = sector_num * BDRV_SECTOR_SIZE;
op->bytes = nb_sectors * BDRV_SECTOR_SIZE;
op->offset = offset;
op->bytes = bytes;
/* Now make a QEMUIOVector taking enough granularity-sized chunks
* from s->buf_free.
@ -298,7 +291,7 @@ static int mirror_do_read(MirrorBlockJob *s, int64_t sector_num,
qemu_iovec_init(&op->qiov, nb_chunks);
while (nb_chunks-- > 0) {
MirrorBuffer *buf = QSIMPLEQ_FIRST(&s->buf_free);
size_t remaining = nb_sectors * BDRV_SECTOR_SIZE - op->qiov.size;
size_t remaining = bytes - op->qiov.size;
QSIMPLEQ_REMOVE_HEAD(&s->buf_free, next);
s->buf_free_count--;
@ -307,12 +300,10 @@ static int mirror_do_read(MirrorBlockJob *s, int64_t sector_num,
/* Copy the dirty cluster. */
s->in_flight++;
s->bytes_in_flight += nb_sectors * BDRV_SECTOR_SIZE;
trace_mirror_one_iteration(s, sector_num * BDRV_SECTOR_SIZE,
nb_sectors * BDRV_SECTOR_SIZE);
s->bytes_in_flight += bytes;
trace_mirror_one_iteration(s, offset, bytes);
blk_aio_preadv(source, sector_num * BDRV_SECTOR_SIZE, &op->qiov, 0,
mirror_read_complete, op);
blk_aio_preadv(source, offset, &op->qiov, 0, mirror_read_complete, op);
return ret;
}
@ -460,8 +451,9 @@ static uint64_t coroutine_fn mirror_iteration(MirrorBlockJob *s)
io_sectors = mirror_clip_sectors(s, sector_num, io_sectors);
switch (mirror_method) {
case MIRROR_METHOD_COPY:
io_sectors = mirror_do_read(s, sector_num, io_sectors);
io_bytes_acct = io_sectors * BDRV_SECTOR_SIZE;
io_bytes_acct = mirror_do_read(s, sector_num * BDRV_SECTOR_SIZE,
io_sectors * BDRV_SECTOR_SIZE);
io_sectors = io_bytes_acct / BDRV_SECTOR_SIZE;
break;
case MIRROR_METHOD_ZERO:
case MIRROR_METHOD_DISCARD: